On Fri, 28 Dec 2018 12:27:59 +0000 "Bernhard M. Wiedemann" <bernhard...@lsmod.de> wrote: > If you run all your tests on the same filesystem, you will get the same > filesystem readdir order, which can make results appear reproducible, when > they are not really. Try running on different ext4 FSes with dir_index > enabled (dir_index is default on). Running in different subdirs on one ext4 > does not suffice, because it uses the same hash-seed. > > > I looked at the diffoscope output and there are definitely ordering > issues visible in the beginning > around "link" and "element" > and later around "cdata" > > Further down you also see many small 1-byte diffs similar to what I had > observed with python-3.6 > so these could be such variations in python's internal refcounts > > Might not matter: We run all our builds with export PYTHONHASHSEED=0 so that > we never get ordering issues from randomized python hashes.
Then lets try again with different ext4-fs. Here is what I tried: $ fallocate -l 2G test.img $ /sbin/mkfs.ext4 test.img $ sudo mount test.img /mnt $ sudo SOURCE_DATE_EPOCH=1545769394 LC_ALL=C.UTF-8 debootstrap --variant=minbase --include=python3 unstable /mnt/debian-unstable $ md5sum /mnt/debian-unstable/usr/lib/python3.7/collections/__pycache__/__init__.cpython-37.pyc df6fe61fe176e4858ce2062233d2280e /mnt/debian-unstable/usr/lib/python3.7/collections/__pycache__/__init__.cpython-37.pyc $ sudo umount /mnt $ rm test.img Then I repeated the above and got the exact same md5sum. Thanks! cheers, josch
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